Rapid exchange balloon catheters are described in U.S. Pat. Nos. 4,762,129 and 5,040,548 which are incorporated herein by reference. These rapid exchange catheters include a distal guidewire lumen which extends through the balloon from a distal end of the balloon to a guidewire exit port proximal of the balloon. In these and other known rapid exchange balloon catheter systems the catheter shafts include a proximal stiff catheter section extending along about 75% of the catheter length and a distal more flexible portion of the catheter between the stiff section and the balloon. The portion of the catheter proximal of the balloon and distal to the stiffer proximal catheter section should be simultaneously very flexible to navigate the coronary arteries, have good column strength to provide pushability, and have good kink resistance. The proximal catheter section generally requires good column strength and less flexibility.
Hypotubes or small metal tubes have been used for the proximal sections of rapid exchange catheters due to their excellent pushability and small wall thickness. Braided catheters can also been used for improved kink resistance.